Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. ănăs, ănătis (gen. plur. anatum, Cic. N. D. 2, 48, 124; Plin. 25, 2, 3, § 6; rarely anatium, Varr. R. R. 3, 5, 14; 3, 11, 1) [kindr. with old Germ. Anut; Lith. antis; mod. Germ. Ente; perh. also with Sanscr. ātis, a waterfowl], f., the duck: greges anatium, Varr. R. R. 3, 11: anatum ova, Cic. N. D. 2, 48, 124 al.: Anas fluviatilis, wild-duck, Ov. M. 11, 773.
2. ănās, ātis, f. [3. anus], disease of old women: anatem morbum anuum dicebant, id est, vetularum sicut senium morbum senum, Paul. ex Fest, p. 29 Müll.; cf. Placid. p. 435 Mai.
3. Ănas, ae, m., a river in Spain, now Guadiana (Arab., i. e. Wadi-Ana, = river Anas), Caes. B. C. 1, 38; Plin. 3, 1, 3, § 3; 4, 22, 35, § 116; Mel. 2, 6; 3, 1; cf. Mann. Hispan. 325.